Device comprising a movable component

ABSTRACT

A device includes an interior which is enclosed by a housing. The housing includes an opening. A movable component closes the opening in the housing between the interior and an exterior of the housing. The passage points for movable components have hydrophobic surfaces. A device of this type is protected in a non-contacting manner against penetration and discharge of fluids.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a device comprising a sealed interior in orderto prevent penetration and/or discharge of fluids, gasses, dust, orbacteria at the points where the movable component closes an opening inthe housing of the device except for an unavoidable gap for the movementof the component.

Brief Description of the Related Art

Sealing of devices against media is a general problem in technology. Ina plurality of applications, a secure function of devices, motors,switches, etc., is necessary under difficult environmental conditions.Such applications are typical for the automotive, nautical, medicaltechnology, and industrial sectors and the like. The penetration ofexternal media into a device often interrupts the device functions.Preventing discharge of media from a device into the surroundings islikewise a typical problem. A plurality of technical solutions is known,for example, for a seal of a device housing at the passage points ofstationary components as well as of movable components.

If the passage of a fixed component is to be permanently sealed understress, then either an additional sealing element or a sealing materialis used. Sealing the passage points of linearly movable and/or rotatingcomponents is particularly demanding. Contact seals at moving componentsare not completely leakproof and generate additional friction on movablecomponents. Known non-contact seals prevent additional friction of thistype; however, they are not completely leakproof. Another possibilityfor sealing is the use of barrier media. However, this type oftechnically leakproof sealing of devices using barrier media at thepassage points of movable components generates additional friction,wherein the design expenses of such seals are also generally greaterthan for other types of seals. Thus, known seals for movable parts upuntil now either are not completely leakproof or generate additionalfriction.

In addition, devices in medical technology or in the food industry areto be protected from germs and toxic substances. Gaps, occurring atmovable components, need to be protected against colonization bybacteria and other microorganisms. Flexible sleeves made from elastomersor films are known from the prior art for sealing these devices. Knownseals are expensive to implement at complete impermeability.

Therefore, there exist a plurality of applications with the desire tofunctionally seal the passage points of movable components at deviceswith respect to external media without impairing the movement of thecomponent.

SUMMARY OF THE INVENTION

The object of the invention is to create a simply designed seal for thepassage points of movable components on a device which functionssecurely, is frictionless, technically leakproof, and, if necessary,antibacterial.

This problem is solved by a housing with the features of claim 1. Thenon-contact seal of the interior is carried out in that surface regionsof the movable component and/or the housing at the passage points of thecomponent, specifically at the openings in the housing of the deviceprovided for these components, are designed to be hydrophobic. Thelinearly and/or rotationally movable components close these openings inthe housing between the interior of the device and the exterior exceptfor an unavoidable gap for the movement. The hydrophobic surfaces arearranged according to the invention parallel to the movement axis of themovable component.

In one preferred embodiment, at least one of the surfaces forming thegap, that is the component-side gap surface or the housing-side gapsurface, is designed to be hydrophobic. Fluids are prevented by thechanged surface tension on the hydrophobically-configured surfaceregions of the gap surfaces at the entry into the gap and thus also atthe entry into the device or at the outlet from the device. In mostcases, it is sufficient to design only one gap surface with ahydrophobic surface.

In the case of a rotating component, the same surface region of thecomponent always delimits the gap and forms the component-side gapsurface. In this type of movable component, the component-side gapsurface and also the housing-side gap surface may be hydrophobic,preferably across the entire gap length. It is also sufficient in thecase of longer gaps to provide partial surfaces of the gap withhydrophobic surfaces.

In the case of a linearly moving component, the surface region of thecomponent delimiting the gap changes due to the displacement of thecomponent in the gap. The component-side gap surface is larger than thehousing-side gap surface, indeed longer by the maximum displacementpath. In the case of this type of linearly movable component,hydrophobic surfaces on the component outside of the gap are thereforealso advantageous, specifically preferably each surface area of thecomponent which delimits the gap during the displacement of thecomponent.

Due to this hydrophobic configuration of surface regions in the area ofthe opening, these surface regions are not wetted by fluids and thuspenetration of fluids through the gap at the passage points of themovable component is prevented. As a result of the so-called Moseseffect, a region above a hydrophobic surface, the cover region, may bemaintained free of a fluid, whereas adjacent surface regions, which arenot hydrophobically configured, may be wetted. The critical height ofthe fluid column, at which a cleared cover region of such a hydrophobicsurface becomes wetted, depends on different factors, for example, thetype of fluid (water, detergent solution, oil, among others), thematerial of the surfaces, if necessary, the polar fraction of thesurface energy, the structure of the surfaces (e.g. nanostructure), orthe coating of the surfaces (hydrophobic substances, like silicic acidbased systems). Depending on the local situations, there arise differentcontact angles of wetting for a fluid drop on a hydrophobic surface anddifferent levels of displacement force. Hydrophobic and superhydrophobicsurfaces are often distinguished, wherein superhydrophobic surfaces areunderstood to have a contact angle of wetting >150°. In thisdescription, hydrophobic and superhydrophobic are not distinguishedbecause these limits are not clearly assigned to physical mechanisms ofaction. The higher the contact angle of wetting, the higher the watercolumn, which may be held back. Contact angles of wetting from 140° to180° are desirable for good functionality of the seals described herefor the gap at movable components. In the case of simpler sealingdemands, 100° may already be sufficient.

If the gap between the movable component and the housing of the device,which is protected by hydrophobic surfaces regions, is less than thecritical height of the water column of the cleared cover regions ofthese hydrophobic surface regions, then the sealing effect is provided.The smaller the gap width, the higher the water column may be, which isheld back. Gap widths of up to 0.2 mm are recommended for gaps at thepassage points.

The best sealing is achieved when two gap surfaces forming a gap areconfigured with hydrophobic surfaces. Hydrophobic surfaces on two sidesof the gap offer optimal sealing in connection with large contact anglesof wetting and small gap widths. Small gap widths and large contactangles of wetting are necessary, in particular for preventing thepenetration of fluids with low surface tensions. For many applications,it is sufficient if only one of the surfaces forming the gap ishydrophobic.

The seal according to the invention is based on the physicalcharacteristics of the surfaces which form the gap. A seal may besecurely implemented when the physical characteristics of thehydrophobic surfaces, the characteristics of the fluid, and the gapgeometry are coordinated with one another. The sealing effect is carriedout in a large range of potential gap widths. Depending on the medium,the arrangement of the hydrophobic surface regions, and the contactangle of wetting of the hydrophobic surfaces, large gap widths are alsoleakproof.

Providing hydrophobic surface regions on the gap surfaces is astructurally simple solution. The simple demands on the geometry resultin large, reliable tolerances at the movable part or the housing andthus simple manufacturing. Such a design may be very robust, whichminimizes the number of potential faults.

No additional component, i.e., no additional sealing element isnecessary for the seal according to the invention, which reduces thematerials used and the weight with respect to the known solutions. Inone particular embodiment, however, it is also possible that at leastone of the hydrophobic surfaces is located on an additional sealingelement and the penetration of fluid into the gap is prevented by thismeans.

The sealing is carried advantageously in a non-contact way. Wear,abrasion, noise, and friction are thus prevented. Despite this, the sealis effective with respect to water and all conventional fluids,including oils, fats, solvents, salt water, water with detergentadditives, etc. The sealing effect is also retained in an advantageousway below a water column.

By using an additional barrier fluid, sealing against gasses is alsopossible.

Sealing by means of hydrophobic surfaces is simultaneously and with noadditional measures also an effective barrier for bacteria, germs, andother microorganisms, since hydrophobic surfaces may not be colonized bybacteria or microorganisms. By using an antiseptic barrier fluid, ahermetic seal is provided against gasses, fluids, dust, and germs.

The invention has the additional advantage that the gaps cleared offluids by means of hydrophobic surfaces are also free of ice during coldtreatment. Ice may not form and adhere to hydrophobic surfaces. Thefunction of the seal may thus not be impaired by ice.

Salt also may not adhere to hydrophobic surfaces. Seals with hydrophobicsurfaces are therefore particularly suitable for seawater and nauticalapplications.

Hydrophobic surfaces of metals are protected from corrosion. Seals,which are generated by metal parts comprising hydrophobic coatings, areprotected from corrosion damage.

The non-contact seal according to the invention may also beretroactively provided in already existing structures, since noadditional sealing element, no extended gap, or other structural changesare necessary. In most cases, a hydrophobization on one side, i.e.either the component-side gap surface or the housing-side gap, isalready sufficient to prevent penetration of fluids through the gap. Alarge multiplicity of technical methods are available to generatehydrophobic surfaces, see “Superhydrophobic coating”, Sandia NationalLaboratories 2008 R&D Award Entry Form, 2007, and “Superhydrophobicmaterials (ORNL)”. If the hydrophobic surface is to be generated, e.g.,by spraying a substrate onto a finished component, then devicesoriginally designed without seals may be retrofitted to be sealeddevices, with changes in the geometry. Some substrates form transparenthydrophobic surfaces, to that the appearance of the treated surfaces isnot changed. The possibility of manufacturing plastic parts whichalready have hydrophobic surfaces using injection molding methods is tobe emphasized, see “Superhydrophobic surfaces on complex injectionmolded parts”, press release from the Institute for Plastics Processingat the RWTH Aachen, March, 2012.

Some embodiments of the invention are subsequently described by way ofthe drawings. Comparable elements are provided with identical referencenumbers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a partial section of a device according to oneembodiment of the present invention.

FIG. 2 illustrates a partial section of the device of FIG. 1 with ascraper.

FIG. 3 illustrates a partial section of the device of FIG. 1 sealed in anon-contact way.

FIG. 4 illustrates another embodiment of a partial section of the deviceof FIG. 1 with an outwardly extending shaft as movable component.

FIG. 5 illustrates yet another embodiment a partial section of thedevice of FIG. 1 with an outwardly extending shaft as movable component.

FIG. 6 illustrates a partial section of an electric switch which formsthe device of FIG. 1.

FIG. 7 illustrates a partial section of the device of FIG. 1 with amotor and a shaft as movable component.

FIG. 8 illustrates a partial section of the device of FIG. 1 with amotor and a shaft as movable component which is provided with acentrifugal disk on the outside of housing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a partial section of a device (1) according to theinvention. Device (1) has an interior (3) which is enclosed by a housing(2). The housing has an opening (4) for a movable component (6).Component (6) may be moved linearly (9) and rotationally (10). Component(6) closes opening (4) except for a gap (31) necessary for the movement.Interior (3) and the exterior (30) are thus connected via gap (31). Thepenetration of fluids through this gap (31) is, however, not possible,since the housing-side gap surfaces (33) delimiting gap (31) have ahydrophobic surface (7), in this case a hydrophobic coating using“Hydrobead®,” or “Never Wet™,” or “Ever Dry®.” The component-side gapsurfaces (32) delimiting gap (31) may additionally or solely behydrophobized in the same way. Gap (31) has in this case a gap width ofless than 1 mm, which securely prevents penetration of water intohousing (2) of device (1).

FIG. 2 shows a partial section of a device (1) which is additionallyprovided with a scraper (11). Device (1) has an interior (3), which isenclosed by a housing (2) and has an opening (4) for a penetratingmovable component (6). Component (6) may also be moved linearly (9) androtationally (10) in this case. The penetration of fluids through gap(31) remaining between component (6) and housing (2) is, however, notpossible, since both housing-side gap surfaces (33) delimiting gap (31)have a hydrophobic surface (7) and also component-side gap surfaces (32)delimiting gap (31) have a hydrophobic surface (8). A scraper (11) isprovided on the outside of housing (2) in the region of opening (4) andis formed by a projecting conical element. The surfaces of theprojecting and conical element are additionally provided withhydrophobic surfaces (7). In this way, solid media and dust areprevented from penetrating through extended gap (31) into interior (3).Outer hydrophobic surfaces (7) on scraper (11) additionally prevent anadhesion of contaminants. Contaminants of this type are transported bythe movable part in the direction of scraper (11). Since thecontaminants may not adhere to scraper (11), they fall down and nolonger impair the movement of component (6).

FIG. 3 shows a partial section of a device (1) likewise sealed in anon-contact way. Technical device (1) has an interior (3) which isenclosed by a housing (2). Housing (2) has in this case two openings(4), specifically for a penetrating fixed component (5) and for apenetrating movable component (6). Housing-side gap surfaces (33), whichform gap (31) between housing (2) and components (5, 6), are providedwith hydrophobic surfaces (7). Component (6) may also be moved linearly(9) and rotationally (10) in this case.

FIG. 4 shows a partial section of a device (1) with an outwardlyextending shaft as movable component (6). This shaft may also be movedlinearly (9) and rotationally (10). Device (1) comprising housing (2)and interior (3) has an opening (4) through which the shaft extendsoutward. Housing (2) has a cavity (14) in the region of opening (4).Cavity (14) is filled with a barrier fluid (15) which forms a surface(16) as a result of the effects of centripetal force (17). Housing-sidegap surfaces (33) and component-side gap surfaces (32) are provided withhydrophobic surfaces (7, 8). These hydrophobic surfaces (7, 8) arethereby arranged such that barrier fluid (15) may not leave cavity (14)and at the same time a circumferential wetting of shaft (6) isguaranteed by barrier fluid (15). Barrier medium (15) is enclosedbetween hydrophobic surfaces (7, 8). In conjunction with centripetalforce (17), a leakproof barrier for gasses is created, as gasses may notpass barrier fluid (15). The sealing of shaft (6) is maintained duringtranslational movements (9), during rotational movements (10), andduring combined translational-rotational movements (9, 10).

FIG. 5 shows the partial section of a device (1), likewise with anoutwardly extending shaft as movable component (6). Unlike device (1)from FIG. 4, centripetal force (17) affects the shaft axially. As isclear, the sealing effect using barrier fluid (15) is maintainedregardless of the effective direction of centripetal force (17).

FIG. 6 shows a partial section of an electric switch which in this caseforms device (1). This electric switch (1) has a housing (2) comprisingan interior (3). A movable component (6), which in this case is anactuating element, protrudes outward through an opening (4) in housing(2). If actuating element (6) executes translational movements (9), thenit is a tappet. If actuating element (6) executes rotational movements(10), then it is a rotary actuator. Combined movements (9, 10) ofactuating element (6) are also possible. Actuating element (6) functionson a switch mechanism (18) which is connected to an electrical circuitvia electrical supply lines (19). Hydrophobic surfaces (7, 8) areprovided in the region of opening (4) in housing (2) for actuatingelement (6) both on component-side gap surfaces (32) and also onhousing-side gap surfaces (33). Due to the potential linear movement ofactuating element (6), hydrophobic surfaces (8) on actuating element (6)are provided past the gap length. This embodiment increases the securityof the seal under harsh real-world conditions. Hydrophobic surfaces (7)are only provided on housing-side gap surfaces (33) in the region ofopening (4) in housing (2) for stationary electrical supply lines (19).This is sufficient for technically conventional gap widths of 0.01-0.3mm. Hydrophobic surfaces (7, 8) prevent a wetting of the surfaces of gapsurfaces (32, 33) delimiting gap (31) and thus a penetration of fluidsinto interior (3) of device (1).

FIG. 7 shows a partial section of a device (1) with a motor (20) and ashaft as movable component (6). Device (1) comprises a housing (2) withan interior (3) in which motor (20) is located. Shaft (6) of motor (20)protrudes outward through opening (4) of housing (2). Housing (2) andshaft (6) are provided with hydrophobic surfaces (7, 8) in the region ofopening (4). Hydrophobic surfaces (7, 8) prevent a wetting of thesurfaces forming gap (31) and thus prevent a penetration of fluids.

FIG. 8 shows a partial section of a device (1) with a motor (20), theshaft of which, designed as movable component (6), is provided with acentrifugal disk (21) on the outside of housing (2). Centrifugal disk(21) amplifies the sealing effect of hydrophobic surfaces (7, 8). Theinward-lying surfaces of housing (2), shaft (6), and centrifugal disk(21) delimiting gap (31) are designed as hydrophobic surfaces (7, 8) andprevent penetration by fluids. The outer, non-hydrophobically coatedparts of centrifugal disk (21) hurl fluid droplets away from shaft (6)due to centrifugal force. Thus, the amount of fluid in the region of gap(31) is largely reduced. A sealing effect is thus ensured in harshenvironmental conditions.

In devices (1) according to FIGS. 1 through 8, a non-contact barrieragainst the penetration of microorganisms is carried out at the sametime. FIGS. 1 through 8 show antibacterial seals, as hydrophobicsurfaces (7, 8) prevent the colonization of bacteria and microorganisms.This is important, in particular, for medical devices. By using anantiseptic barrier fluid (15) in FIG. 4 and FIG. 5, a migration of germsthrough barrier fluid (15) is prevented, in addition to gas penetration.Barrier fluid (15) blocks the air path, functions antiseptically, and isenclosed between hydrophobic surfaces (7, 8). Regardless of the effectof centripetal force, a leakproof barrier is created, which blocks apenetration of air with bacteria, germs, and microorganisms, and apenetration of dust through gap (31).

REFERENCE NUMERALS

-   1 Device-   2 Housing-   3 Interior-   4 Opening-   5 Stationary component-   6 Movable component-   7 Hydrophobic surface, housing-   8 Hydrophobic surface, component-   9 Linear movement direction-   10 Direction of rotation-   11 Scraper-   14 Cavity-   15 Barrier fluid-   16 Barrier fluid surface-   17 Direction of centripetal force-   18 Electric switch mechanism-   19 Electrical supply line-   20 Motor-   21 Centrifugal disk-   30 Exterior-   31 Gap-   32 Component-side gap surface-   33 Housing-side gap surface

The invention claimed is:
 1. A device, comprising: a housing comprisingat least one opening; a movable component closing the at least oneopening of the housing up to a gap between the housing and the movablecomponent forming a non-contact seal, the gap defining a housing-sidegap surface and a component-side gap surface and the gap being free ofany sealing element between the housing and the movable component andpreventing penetration of fluids through the gap; wherein one of thecomponent-side gap surface and the housing-side gap surface is providedwith a hydrophobic surface, and another of the component-side gapsurface and the housing-side gap surface is provided with anon-hydrophobic surface.
 2. The device according to claim 1, wherein thehousing-side gap surface is covered by the hydrophobic surface.
 3. Thedevice according to claim 1, wherein the movable component is movablelinearly and an axial length of the hydrophobic surface of thecomponent-side gap surface is greater than an axial length of the gap inthat the hydrophobic surface extends to each region of thecomponent-side gap surface which delimits the gap during a lineardisplacement of the movable component.
 4. The device according to claim1, wherein a scraper with the hydrophobic surfaces is arranged aroundthe movable component on a side of the housing.
 5. The device accordingto claim 1, wherein an additional fluid barrier is provided for agas-tight sealing of the housing, the additional fluid barrier comprisesat least one receptacle in a cavity in at least one gap surface and abarrier fluid is retained in the cavity.
 6. The device according toclaim 5, wherein the barrier fluid is antiseptic.
 7. The deviceaccording to claim 1, wherein an electric switching mechanism isprovided in the housing and is connected to electrical connections andis connected to the movable component functioning as an actuatingelement, wherein openings for the electrical connections and for themovable component are provided in the housing, and wherein at least oneof the gap surfaces of the gap between the connections and the housinghas hydrophobic surfaces.
 8. The device according to claim 1, wherein amotor is provided in the housing and is connected to the movablecomponent designed as a shaft, wherein the at least one opening isprovided in the housing for the movable component.
 9. The deviceaccording to claim 8, wherein the movable component designed as theshaft is provided with a centrifugal disk out of the housing, wherein aninner surface of the centrifugal disk and/or an outer side of thehousing in the region of the centrifugal disk have the hydrophobicsurfaces.
 10. The device according to claim 1, wherein additionalopenings are provided in the housing for a stationary component, whereinone of the surfaces forming the gap is provided with a hydrophobicsurface.
 11. The device according to claim 1, wherein the hydrophobicsurface is provided with a hydrophobic coating or has a correspondingnanostructure.
 12. A device, comprising: a housing comprising at leastone opening; a movable component closing the at least one opening of thehousing; and a gap formed between the housing and the movable componentand defining a housing-side gap surface and a component-side gap surfaceand the gap being free of any sealing element between the housing andthe movable component and preventing penetration of fluids through thegap; wherein one of the housing-side gap surface and the component-sidegap surface is provided with a hydrophobic surface, and another of thecomponent-side gap surface and the housing-side gap surface is providedwith a non-hydrophobic surface; and an electric switching mechanism isprovided in the housing and is connected to electrical connections andis connected to the movable component functioning as an actuatingelement, wherein openings for the electrical connections and for themovable component are provided in the housing, and wherein at least oneof the gap surfaces of the gap between the connections and the housinghas hydrophobic surfaces.
 13. A device, comprising: a housing comprisingat least one opening; a movable component closing the at least oneopening of the housing; and a gap formed between the housing and themovable component and defining a housing-side gap surface and acomponent-side gap surface and the gap being free of any sealing elementbetween the housing and the movable component and preventing penetrationof fluids through the gap; wherein one of the housing-side gap surfaceand the component-side gap surface is provided with a hydrophobicsurface, and another of the component-side gap surface and thehousing-side gap surface is provided with a non-hydrophobic surface; anda motor is provided in the housing and is connected to the movablecomponent designed as a shaft, wherein the at least one opening isprovided in the housing for the movable component.
 14. A device,comprising: a housing comprising at least one opening; a movablecomponent closing the at least one opening of the housing; and a gapformed between the housing and the movable component and defining ahousing-side gap surface and a component-side gap surface and the gapbeing free of any sealing element between the housing and the movablecomponent and preventing penetration of fluids through the gap; whereinone of the housing-side gap surface the component-side gap surface isprovided with a hydrophobic surface, and another of the component-sidegap surface and the housing-side gap surface is provided with anon-hydrophobic surface; and wherein additional openings are provided inthe housing for a stationary component, wherein one of the surfacesforming the gap is provided with a hydrophobic surface.